Life is sacred. That doesn't mean, however, that honouring that sacredness means that life has to be preserved at all costs in all situations. To do so robs people of their dignity and makes them suffer in ways that wouldn't even be considered necessary if it weren't for the religious excuses that are so often held up as reasons to make it happen. And honouring the sanctity of life doesn't necessarily mean the preservation of Earthly existence; sometimes, when the most compassionate thing to do is to let that life end, or to cause it to end, then honouring the sanctity of life means accepting the reality of death.
"Everything that has a beginning has an end."
—The Oracle, "The Matrix Revolutions"